- A
Layer 2
Why wrong: Layer 2 (Data Link) encapsulates the packet into a frame with MAC addresses, not IP addresses. IP addressing is a Layer 3 function.
- B
Layer 3
The network layer (Layer 3) adds the IP header containing source and destination IP addresses. This is where logical addressing occurs, enabling routing across networks.
- C
Layer 4
Why wrong: Layer 4 (Transport) encapsulates data into segments or datagrams with port numbers for upper-layer services. IP addressing is not added at this layer.
- D
Layer 1
Why wrong: Layer 1 (Physical) deals with the actual transmission of bits over the medium. No headers are added at this layer.
Question 348 of 520
N10-009 Networking Concepts Practice Question
This N10-009 practice question tests your understanding of networking concepts. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network technician is explaining the concept of encapsulation to a junior technician. At which OSI layer does a packet get encapsulated with a source and destination IP address?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Layer 3
At Layer 3 (the Network layer), the packet is encapsulated with a source and destination IP address. This is defined by the Internet Protocol (IP), which handles logical addressing and routing across networks. The IP header is added to the payload from the upper layers, creating a packet that can be forwarded by routers.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Layer 2
Why it's wrong here
Layer 2 (Data Link) encapsulates the packet into a frame with MAC addresses, not IP addresses. IP addressing is a Layer 3 function.
When this WOULD be correct
This option would be correct if the question asked: 'At which OSI layer does a frame get encapsulated with source and destination MAC addresses?'
- ✓
Layer 3
Why this is correct
The network layer (Layer 3) adds the IP header containing source and destination IP addresses. This is where logical addressing occurs, enabling routing across networks.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Layer 4
Why it's wrong here
Layer 4 (Transport) encapsulates data into segments or datagrams with port numbers for upper-layer services. IP addressing is not added at this layer.
When this WOULD be correct
A question asking 'At which OSI layer is a segment encapsulated with source and destination port numbers?' would make Layer 4 correct.
- ✗
Layer 1
Why it's wrong here
Layer 1 (Physical) deals with the actual transmission of bits over the medium. No headers are added at this layer.
When this WOULD be correct
A question asking at which layer data is converted into electrical signals, light pulses, or radio waves for transmission over a physical medium would have Layer 1 as the correct answer.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓Layer 3Correct answer▾
Why this is correct
The network layer (Layer 3) adds the IP header containing source and destination IP addresses. This is where logical addressing occurs, enabling routing across networks.
✗Layer 2Wrong answer — click to see why▾
Why this is wrong here
Layer 2 (Data Link layer) uses MAC addresses for local network delivery, not IP addresses. Encapsulation with source and destination IP addresses occurs at Layer 3 (Network layer).
★ When this WOULD be the correct answer
This option would be correct if the question asked: 'At which OSI layer does a frame get encapsulated with source and destination MAC addresses?'
Why candidates choose this
Candidates often confuse the roles of Layer 2 and Layer 3, mistakenly thinking IP addresses are added at Layer 2 because both involve addressing.
✗Layer 4Wrong answer — click to see why▾
Why this is wrong here
Layer 4 (Transport) uses port numbers and manages end-to-end communication, not IP addressing. IP addresses are added at Layer 3 (Network).
★ When this WOULD be the correct answer
A question asking 'At which OSI layer is a segment encapsulated with source and destination port numbers?' would make Layer 4 correct.
Why candidates choose this
Candidates may confuse encapsulation of IP addresses with the Transport layer because TCP/UDP headers also contain addressing information (ports), leading to a mix-up between network and transport addressing.
✗Layer 1Wrong answer — click to see why▾
Why this is wrong here
Layer 1 (Physical) deals with raw bit transmission over physical media, not with IP addresses. Encapsulation with IP addresses occurs at Layer 3 (Network).
★ When this WOULD be the correct answer
A question asking at which layer data is converted into electrical signals, light pulses, or radio waves for transmission over a physical medium would have Layer 1 as the correct answer.
Why candidates choose this
Candidates may confuse the physical transmission of data with the encapsulation process, thinking that IP addresses are added at the lowest layer because they associate addressing with hardware interfaces.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Layer 2 MAC addressing with Layer 3 IP addressing, mistakenly thinking the packet is encapsulated with IP addresses at the Data Link layer, but encapsulation with IP addresses occurs strictly at the Network layer.
Detailed technical explanation
How to think about this question
The IP header includes fields like version (IPv4 or IPv6), TTL, protocol, and checksum, in addition to source and destination IP addresses. In IPv4, the header is typically 20 bytes (without options), and the packet is the PDU at Layer 3. A real-world scenario: when a host sends data to a remote server, the IP address is used by routers to make forwarding decisions based on the routing table, while MAC addresses are only relevant within a single broadcast domain.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the N10-009 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Quick reference
OSI Model Reference
| Layer | Name | PDU | Key Protocols / Devices |
|---|---|---|---|
| 7 | Application | Data | HTTP, HTTPS, DNS, SMTP, FTP, SSH |
| 6 | Presentation | Data | TLS / SSL, JPEG, ASCII encoding |
| 5 | Session | Data | NetBIOS, RPC, SIP |
| 4 | Transport | Segment / Datagram | TCP, UDP |
| 3 | Network | Packet | IP, ICMP, OSPF — Routers |
| 2 | Data Link | Frame | Ethernet, Wi-Fi, PPP — Switches, Bridges |
| 1 | Physical | Bits | Cables, NICs, Hubs, Repeaters |
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this N10-009 question test?
Networking Concepts — This question tests Networking Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Layer 3 — At Layer 3 (the Network layer), the packet is encapsulated with a source and destination IP address. This is defined by the Internet Protocol (IP), which handles logical addressing and routing across networks. The IP header is added to the payload from the upper layers, creating a packet that can be forwarded by routers.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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Last reviewed: Jun 11, 2026
This N10-009 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the N10-009 exam.
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